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What is a Graded-Index Fiber?
A Graded-Index fiber is an optical fiber in which the refractive index gradually decreases from the center of the core toward the cladding. Unlike a step-index fiber, this gradual refractive index profile causes light rays to follow curved paths through the core.
Graded-index fibers are particularly useful for multimode transmission, where they help reduce modal dispersion and improve bandwidth compared with conventional step-index multimode fibers.
HOW a Graded-Index Fiber Works
A Graded-Index fiber guides light through a gradual variation in refractive index across the core. This profile causes different modes to travel at different speeds in a way that reduces the difference in their propagation times.
Gradual index variation
The refractive index is highest near the center of the core and progressively decreases toward the cladding.
Curved light propagation
Instead of following primarily zigzag paths, light rays continuously bend as they travel through regions with different refractive indices.
Reduced modal dispersion
Higher-order modes generally travel through lower-index regions and follow longer paths, while lower-order modes remain closer to the higher-index center. This helps reduce differences in propagation time and increases the achievable bandwidth.
